The Sampradaya Parishuddhi is a work by the 13th century Sri Vaishnava Acharya Vedanta Desikan defending the flawless nature of the Sri Vaishnava Sampradayam. He discusses many incidents in Sri Vaishnava history, including how Yamunacharya, aka Alavandar, was reformed. In his youth Yamunacharya, grandson of the Sri Vaishnava Acharya Nathamuni, became king of half the Pandya empire, and he spent a large part as king. But then Manakkal Nambi, who was Nathamuni’s shishya’s shishya, used various tactics to rekindle Yamunacharya’s interest in Sri Vaishnavism, until Yamunacharya became Manakkal Nambi’s shishya. Now the question arises, why did Manakkal Nambi seek out Yamunacharya as a shishya, when scripture says that shishyas should seek out Acharyas and not the other way around? But Vedanta Desikan explains how Manakkal Nambi’s actions were justified:
maṇakkāl nampi āḷavantārukku neṭunāḷ paccaiyiṭṭu, oru virakālē ākāṅkaivu uṇṭākki upatēcittatu - ācārya kulattiṟkut tāmoru kiñcit kāram paṇṇukaiyilum paramācārya niyō kattaik kaṭukat talaikkaṭṭukaiyilu muṇ ṭāṉa tvaraiyālum, cirakāla-parīkṣādikaḷ vēṇṭātapaṭi “bodhanaṃ ca muhuḥ kramāta” eṉkiṟa yugadharma anusārattālum upapannam
Manakkal Nambi imparted spiritual knowledge to Alavandar in him by a device viz. supplying for a long time leaves which were used as a dish in his food. Manakkal Nambi is not inconsistent with the Sastra; because had a great eagerness to do some service to the race of his Acharya and to carry out the command of his own Acharya without any delay. Again this is in accordance with the procedure in the Kaliyuga by which the disciple need not be subjected to any preliminary tests extending over long periods as stated in the following text: "Instruction should be given repeatedly and step by step."
I’m interested in the part in bold. My question is, what scriptures say that Acharyas in the Kali Yuga do not need to subject their shishyas to preliminary tests extending over long periods of time?
Also, what is the “bodhanaṃ ca muhuḥ kramāta” verse from? Is it a verse laying out the Kali Yuga rule Vedanta Desikan alludes to, or is it laying out the more restrictive rule followed in earlier Yugas,? Do any commentaries on the Sampradaya Parishuddhi shed light on this?